Ink jet printing systems are known in which a printhead defines one or more rows of orifices which receive an electrically conductive recording fluid from a pressurized fluid supply manifold and eject the fluid in rows of parallel streams. Printers using such printheads accomplish graphic reproduction by selectively charging and deflecting the drops in each of the streams and depositing at least some of the drops on a print receiving medium, while others of the drops strike a drop catcher device.
Over the years, a number of inkjet printers using binary array continuous inkjet printing have been developed, with continuing improvements in speed, reliability, and ease of use. These printers are used in a variety of print applications, often using aqueous inks. Using aqueous ink, these printers can print for hours and have demonstrated highly reliable shutdown and subsequent startups without operator intervention. In spite of advances in aqueous ink technology, solvent inks, such as ethanol or MEK based inks, are preferred for some applications. For example, in applications such as printing on metals or plastics, solvent inks are preferred over aqueous inks as a result of the solvent ink characteristics of being much faster drying and more permanent than aqueous inks.
The same characteristics that make solvent inks preferred for printing on metals and plastics, however, make solvent inks much harder to run in inkjet printers. Just as the inks dry quickly on the print media, they also dry quickly on the various components in an inkjet printhead and fluid system. In particular, these inks can dry quickly on the orifice plate and the charge plate in the printhead. On the orifice plate, the dried ink can plug the orifices through which the ink is to be jetted, adversely interfering with jet directionality. When dried on the charge plate, the dried ink can produce shorting conditions between charging electrodes.
As a result of these problems, prior art inkjet printers using solvent inks have required significant intervention by highly trained operators, for proper operation both when the printers are started and shutdown. There is a need for a printer for use with highly volatile solvent based inks which can be shut down in a manner that will allow subsequent reliable start up.